1. Technical Field
Mechanically actuated substance delivery methods and systems, including implantable, pressure-actuated drug delivery methods and systems.
2. Related Art
Coronary stents are commonly used to treat heart attacks. Stents, however, have been known to abruptly clot. Conventional stent clot treatment includes emergency angioplasty, which is expensive, difficult to coordinate, and accompanied by relatively high mortality rates.
Stents have been coated with drugs (“drug-eluting stents”) to reduce the formation of scar tissue. However, drug-eluting stents have been shown to increase the likelihood of abrupt in-stent clot formation.
Stents have been textured and coated with antibodies and proteins to attract native cell coverings in attempts to promote vessel healing and reduce clot formation, without much success and, in some cases, with increased clotting. Furthermore, such passive systems are not able to sense nor adapt to new clots that may occur.
Conventional intracoronary drug-delivery systems are passive. Drugs are released with pre-determined kinetics, and these systems cannot sense nor respond to new, abrupt environmental changes such as clotting. Active drug delivery systems deliver drugs in response to an external stimulus, but conventional systems require a bulky or externalized power source, a separate sensor and are unsuitable for intracoronary application. For example, World Intellectual Property Organization (WIPO) publication number WO 2007/042961, to Johnson et al., teaches a substrate having a chemical containing reservoir sealed with a rupturable barrier layer (Johnson, page 2, lines 18-26), including a polymer layer and a metal layer (Johnson, page 6, lines 1-10), and an “inkjet printer and/or hydraulic system (i.e., a fluid pressure system with controlled release valves),” or a “piezo-electrical means, e.g. a piezoactuator and/or loudspeaker,” (Johnson, page 5, lines 21-29), to rupture the barrier layer.
What are needed are small-scale, implantable, minimally invasive, and mechanically actuated drug delivery methods and systems that do not require an external power source or a separate sensor.